Regional anesthesia (RA) is a powerful technique to reduce both perioperative and chronic pain. RA provides significant benefits to patients since it requires only light sedation and thereby results in a low incidence of postoperative complications. Despite these advantages, only 5-20 percent of eligible patients receives RA. Selection for RA depends primarily on a practitioner's confidence in applying the method. The proposed research will develop a device that will improve physician confidence by providing realtime feedback during RA. The success of the block: depends on locating the deeply placed nerves for peripheral nerve blockade or the neurovaseular bundle for plexus blockade, while avoiding surrounding vital structures. Since target nerves lie in close proximity to major blood vessels, guidance will be provided using a combination of Doppler ultrasound (for long-range direction) and electrical nerve stimulation for confirmation of needle placement. A Doppler Directed Nerve Stimulator (DDNS) using the continuous-wave Doppler method will be built and a clinical study undertaken to study its efficacy for guiding RA. A DDNS prototype using pulsed-wave Doppler will be built and tested for improved performance and safe about. Successful completion of Phase II will lead to the introduction of a new product for RA delivery. PROPOSED COMMERCIAL APPLICATION: RA potentially benefits both patients and payers since its use promotes rapid recovery, shortened hospital stays and excellent pain control. The overall cost of RA is about 1/3 of costs associated with general anesthesia. The development of a disposable device for guiding RA will result in a commercially viable product, which will increase the use of RA and decrease the costs associated with surgical anesthesia and post-operative care.